Vertical axis wind turbine

Abstract

A vertical axis wind turbine with blades which articulate to reduce drag when they are moving upwind and which are suitable for use in small scale electrical generators. The turbine has blades which are rotatable about a blade axis of rotation and the blade axis is rotatable about a turbine axis of rotation. A vane is coupled to the blade axis of rotation to change the orientation of the blades in response to changes in wind direction. The vane maximizes the effect of the wind on the one or more blade by adjusting the blade position to maximize the blade surface area facing into the wind when the blade is moving downwind and to minimize the blade surface area facing into the wind when the blade is moving upwind.

1 . A vertical axis wind turbine comprising:
 one or more turbine blades being rotatable about a blade axis of rotation said blade axis being mounted for rotation about a turbine axis of rotation, and;   blade orientation means comprising a coupling which is connected between the blade axis of rotation and a vane axis which is coaxial with but decoupled from the turbine axis of rotation, such that, for a given wind direction, the blade orientation means maximises the effect of the wind on the one or more blade by adjusting the blade position to maximise the blade surface area facing into the wind when the blade is moving downwind and to minimise said blade surface area facing into the wind when the blade is moving upwind; and   a wind vane attached to the vane axis so as to change the overall orientation of the wind turbine in response to a change in wind direction to maintain the maximised performance of the one or more blade,   wherein the coupling comprises a first wheel mounted upon the blade axis of rotation and a second wheel mounted on the vane axis which are connected by a closed loop circumferentially mounted on the wheels and a belt drive and the orientation of the wind vane relative to the belt drive is biased to compensate for the torque applied to the belt drive.   
     
     
         2 . A vertical axis wind turbine as claimed in  claim 1  wherein, the coupling aligns the blades substantially perpendicular to the wind when they are on the downwind side of the turbine and substantially parallel to the wind on the upwind side. 
     
     
         3 . A vertical axis wind turbine as claimed in  claim 1  wherein, the coupling is arranged to provide counter-rotation of the blades at half the rate of rotation of the frame. 
     
     
         4 . (canceled) 
     
     
         5 . A vertical axis wind turbine as claimed in  claim 1  wherein, the first wheel comprises a blade cog connected to the blade axis of rotation the second wheel comprises a central cog coaxially mounted on the vane axis and the closed loop comprises a belt with cog engaging means connected between the blade cog and central cog, 
     
     
         6 . A vertical axis wind turbine as claimed in  claim 5  wherein, the first wheel has a diameter twice that of the second wheel. 
     
     
         7 . (canceled) 
     
     
         8 . A wind turbine as claimed in  claim 6  wherein, the wind vane is coupled to the second wheel. 
     
     
         9 . A wind turbine as claimed in  claim 1  further comprising a frame upon which the one or more turbine blades and the central turbine axis are rotatably mounted and to which the wind vane and blade orientation means are fixed. 
     
     
         10 . A wind turbine as claimed in  claim 1  wherein, the wind vane is positioned inside the frame. 
     
     
         11 . A wind turbine as claimed in  claim 1  wherein, the wind vane is positioned inside the radial and/or axial extent of the one or more blade. 
     
     
         12 . A wind turbine as claimed in  claim 10  wherein, the wind vane is positioned asymmetrically on or near the frame with respect to the vane axis so that the vane remains downwind relative to any wind direction. 
     
     
         13 . (canceled) 
     
     
         14 . A wind turbine as claimed in  claim 1 , the wind vane is shaped so as to deflect the wind in the direction of rotation of the frame. 
     
     
         15 . A wind turbine as claimed in  claim 1  wherein, the wind vane is provided with dampening means to inhibit oscillation of the vane about an equilibrium position for a given wind direction. 
     
     
         16 . A wind turbine as claimed in  claim 15  wherein, the dampening means is a rotary dashpot. 
     
     
         17 . A wind turbine as claimed in  claim 1  wherein the one or more turbine blade is symmetrical under 180 degree rotation about its blade axis. 
     
     
         18 . A wind turbine as claimed in  claim 1  wherein, the one or more turbine blade has a substantially flat profile 
     
     
         19 . A wind turbine as claimed in  claim 1  wherein, the blade axis of rotation is tilted. 
     
     
         20 . A wind turbine as claimed in  claim 19  wherein, the blade axis of rotation may be tilted radially and/or circumferentially. 
     
     
         21 . A wind turbine as claimed in  claim 20  wherein, the turbine blade has a cross-sectional shape which produces lift forces which reinforce the rotation of the turbine. 
     
     
         22 . A wind turbine as claimed in  claim 1  further comprising an electrical generator. 
     
     
         23 . A wind turbine as claimed in  claim 1  further comprising an output shaft. 
     
     
         24 . A wind turbine as claimed in  claim 1  wherein, a single toothed belt engages with the blade cog, the central cog and also an accelerator pulley attached to the frame, wherein:
 the rear of the belt may engage with one or more idler pulleys; 
 the accelerator pulley is attached coaxially to an accelerator gear; 
 the accelerator gear engages an output gear, coaxial with the turbine axis; 
 the output gear is attached coaxially to the output shaft. 
 
     
     
         25 . A wind turbine as claimed in  claim 1  wherein, a two-sided toothed belt engages with the blade cog, the central cog and an accelerator pulley attached to the frame, wherein:
 the accelerator pulley is attached coaxially to a second accelerator pulley; 
 the second accelerator pulley is linked by a further belt to an output pulley, coaxial with the turbine axis; 
 the output pulley is attached coaxially to the output shaft. 
 
     
     
         26 . A wind turbine as claimed in  claim 1  wherein a two-sided toothed belt and one or more single-sided toothed belts engage with the blade pulleys, the central pulleys and a third accelerator pulley attached to the frame, wherein:
 the third accelerator pulley is attached coaxially to a fourth accelerator pulley; 
 the fourth accelerator pulley is linked by a further belt to an output pulley, coaxial with the turbine axis; 
 the output pulley is attached coaxially to the output shaft. 
 
     
     
         27 . A wind turbine as claimed in  claim 1  wherein, the frame is shaped to funnel wind onto the one or more blade. 
     
     
         28 . A wind turbine as claimed in  claim 1  wherein, the vertical axis wind turbine comprises two frames each attached to one or more blades, counter-rotating about a common turbine axis.